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2 Physicochemical Problems of Mineral Processing

2 2020

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Microbial synthesis of unique nanoscale minerals - challenges and prospects

Maliszewska Irena, Kocek Daria, Wanarska Ewelina

Physicochemical Problems of Mineral Processing

2020

Vol. 56, iss. 6

244--256

In this review, we highlight new insights and place the molecular mechanisms of the biogenesis of nanomaterials such as silicified frustules, coccoliths, magnetosomes and bacterial nanowires in the context of the complex biology of a microbial cell. The silicified frustules are formed by diatoms, which are a widespread group of organisms found in the oceans, fresh water, soil and wet surfaces. They are especially important in the oceans, where it is estimated that they contribute to 45% of total primary ocean production. Coccolith is a collective term that designates all of the biomineralized, calcified scales produced by extant and extinct haptophytes (single-celled algae). The orientation of magnetotactic bacteria is based on the presence of unique organelles, magnetosomes, which are intracellular, membrane-enclosed, nanometre-sized crystals of magnetic iron minerals. The discovery of bacterial conductive structures, called nanowires, has fascinated scientists for almost a decade. Nanowires enable bacteria to transfer electrons over micrometer distances to extracellular electron acceptors such as insoluble metal oxides or electrodes. The possible applications of these extremely interesting nanomaterials in different areas of life is also considered.

Gold nanoparticles in an enhancement of antimicrobial activity

Wanarska Ewelina, Maliszewska Irena

Physicochemical Problems of Mineral Processing

2020

Vol. 56, iss. 6

269--279

The effect of antimicrobial photodynamic therapy (aPDT) on Gram-positive bacterium Staphylocccus aureus was studied. Methylene blue (MB) at non-toxic concentration of 31.25µg/ml was used as a photosensitizer. LEDs diodes were used as a light source to study the effect of methylene blue alone and the MB-gold nanoparticle mixture on the viability of S. aureus cells. Biogenic gold nanoparticles (biolAuNPs, 10ppm) and chemically synthesized gold nanoparticles (chemAuNPs, 3ppm) were tested as enhancement agents. In the presence of MB alone as a photosensitizer, the killing effect was about 92% after 30min of irradiation. The aPDT therapy was enhanced by addition of biolAuNPs and chemAuNPs and killing rate of S. aureus was 95-96% after 30min of irradiation. The probable mechanism of enhancement of MB-mediated photodynamic bactericidal efficacy against S. aureus in the presence of gold nanoparticles is discussed leading to the conclusion that colloidal gold increases the accumulation of MB in bacterial cells.